Objective To detect early diagnosis significance of cardiopulmonary exercise test in idiopathic pulmonary fibrosis(IPF).Methods 32 cases of IPF were individed into 2 groups,early-stage group (19cases) and non-early-stage group (13cases).All IPF patients and 22 healthy persons as control were performed cardiopulmonary exercise test.Results All indexes of cardiopulmonary exercise test were significantly different between the early-stage group and the control group,the non-early-stage group and the control group,the non-early-stage group and the early-stage group.Conclusion Cardiopulmonary exercise test markedly raises value early diagnosis in IPF.